Total Thyroxine (TT4)
Total T4
Testing Information
Sample Type
Serum
Test Codes
650730
CPT Code
84436
Testing Area
Core Lab - Chemistry
Test Methodology
Abbott Alinity - Chemiluminescence Immunoassay
Reference Range
4.5-12.0 ug/dL
Expected Turnaround Time
Results Available 24 hours from Receipt
Specimen Collection Criteria
Collect one gold top SST tube (minimum whole blood: 4 mL). Let specimen clot for 30-60 minutes and then centrifuge to separate serum from cells. Refrigerate after centrifugation.
Rejection Criteria
Grossly hemolyzed specimens, quantity not sufficient, improperly labeled
Specimen Validity and Retention
Centrifuged SST Tubes:Room Temperature (20-25°C): 2-4 hoursRefrigerated (2-8°C): 7 daysFrozen (-20°C or greater): UnacceptableSerum Aliquots:Room Temperature (20-25°C): 2-4 hoursRefrigerated (2-8°C): 7 daysFrozen (-20°C or greater): 7 daysSpecimens retained for 7 days after testing
Courier Transportation
Transport centrifuged tube refrigerated (2-8°C)
Clinical Utility
Total T4 assay is a thyroid function test. It is typically used to support diagnosis of thyrotoxicosis and hyperthyroidism.
Special Notes
Stop Biotin supplements?
